INTRODUCTION

Science based on research towards the development of new sustainable processes

DEFINITION Defined as the invention, design and

application of chemical products and processes to reduce or to eliminate the use and generation of hazardous substances

SIGNIFICANCE

Major tool in accomplishing Pollution prevention

Leads to reduction in waste

Reduced use of energy and other perishable resources

Carrying out chemical activities leading to safer products

PRINCIPLES OF GREEN CHEMISTRY

Term coined by Dr. Paul Anastas known as the “Father of Green Chemistry”

He defined it as the utilization of a set of principles that reduces or eliminates the use or generation of hazardous substances in the design, manufacture and application of chemical products

12 PRINCIPLES OF GREEN CHEMISTRY

1. Prevent waste2. Atom Economy3. Less Hazardous Chemical

Synthesis 4. Designing Safer Chemicals5. Use safer Solvents /reaction

conditions6. Increase Energy Efficiency. 7. Use of Renewable Feedstocks 8. Reduce chemical derivatives9. Use catalysts10. Design for Degradation11. Real-time Analysis for Pollution

Prevention.12. Inherently Safer Chemistry for

Accident Prevention

1. PREVENT WASTE

Design processes which minimize waste Better to prevent waste than to clean and treat

it

2. ATOM ECONOMY

Atom economy =Mass of atoms in desired product x 100

Mass of atoms in reactants Concept developed by Barry Frost Evaluates the efficiency of a chemical transformation

ATOM ECONOMY

Choose transformations that incorporate most of the starting materials into the product increases the efficiency and minimizes waste

3. LESS HAZARDOUS CHEMICAL SYNTHESIS

Wherever practicable, synthetic methodologies should be designed to use and generate substances that possess little or no toxicity to human health and the environment

LESS HAZARDOUS CHEMICAL SYNTHESIS Polycarbonate Synthesis: Phosgene Process

Disadvantages phosgene is highly toxic, corrosive requires large amount of CH2Cl2 polycarbonate contaminated with Cl

impurities

OH OHCl Cl

O

+NaOH

O O *

O

* n

LESS HAZARDOUS CHEMICAL SYNTHESIS Polycarbonate Synthesis: Solid-State Process

Advantages diphenylcarbonate synthesized without

phosgene eliminates use of CH2Cl2 higher-quality polycarbonates

OH OH

+ O O *

O

* n

O O

O

4. DESIGNING SAFER CHEMICALS

Chemical products should be designed to preserve efficacy of the function while reducing toxicity

DESIGNING SAFER CHEMICALS

Antifoulants are generally dispersed in the paint as it is applied to the hull. 

Organotin compounds have traditionally been used, particularly tributyltin oxide (TBTO). 

TBTO works by gradually leaching from the hull killing the fouling organisms in the surrounding area

Organotin compounds are chronically toxic to marine life and can enter food chain. They are bioaccumulative.

5. USE SAFER SOLVENTS/REACTION CONDITIONS

The use of auxiliary substances (solvents, separation agents, etc.) should be made unnecessary whenever possible and, when used, innocuous.

USE SAFER SOLVENTS/REACTION CONDITIONS

Solvent Substitution Water as a solvent New solvents

Ionic liquids Supercritical fluids

6. INCREASE ENERGY EFFICIENCY.

Energy requirements should be recognized for their environmental and economic impacts and should be minimized. Synthetic methods should be conducted at ambient temperature and pressure

7. USE OF RENEWABLE FEEDSTOCKS

A raw material or feedstock should be renewable rather than depleting whenever technically and economically practical

RAW MATERIALS FROM RENEWABLE RESOURCES:THE BIOFINE PROCESS

O

HO

O

Paper mill sludge

Levulinic acid

Municipal solid wasteand waste paper

Agricultural residues,Waste wood

Green Chemistry Challenge Award1999 Small Business Award

LEVULINIC ACID AS A PLATFORM CHEMICAL

O

HO

O

O

H2N

OH

O

O

HO

DALA (-amino levulinic acid)(non-toxic, biodegradable herbicide)

O

HO

O

OH

C

CH3

CH2

CH2

C

O

OHHO

Diphenolic acid

Acrylic acidSuccinic acid

O

THF

O

MTHF(fuel additive)

HO

OH

butanediol

OO

gamma butyrolactone

8. REDUCE CHEMICAL DERIVATIVES

Unnecessary derivatisation (blocking group, protection/ de-protection, temporary modification of physical/chemical processes) should be avoided whenever possible

Reduces atom economy

Increases waste

9. USE CATALYSTS

Catalytic reagents (as selective as possible) are superior to stoichiometric reagents

Readily regenerated, separated

Recyclable

Mild conditions

10. DESIGN FOR DEGRADATION

Chemical products should be designed so that at the end of their function they do not persist in the environment and instead break down into innocuous degradation products

CFCs, DDT Biodegradable polymers

11. REAL-TIME ANALYSIS FOR POLLUTION PREVENTION

Analytical methodologies need to be further developed to allow for real-time in-process monitoring and control prior to the formation of hazardous substances

Real time analysis for a chemist is the process of “checking the progress of chemical reactions as it happens.”

Knowing when your product is “done” can save a lot of waste, time and energy!

12. INHERENTLY SAFER CHEMISTRY FOR ACCIDENT PREVENTION

Substance and the form of a substance used in a chemical process should be chosen so as to minimize the potential for chemical accidents, including releases, explosions, and fires

Various industrial accidents

Eg: Bhopal gas tragedy

GREEN CATALYSTS